How to Build and Fly the ½ A TEXACO POWERHOUSE

How to Build and Fly the ½ A TEXACO POWERHOUSE
By Gary Sherman
I am frequently asked what makes a good first free
flight model to build and fly. In my opinion, there is
no better model than Sal Taibi’s 1/2A Texaco
Powerhouse and it is a good choice for several
reasons. Almost any 1/2A engine will work well to
power it, especially any of the Cox product engines
or Texaco engine (these are especially easy to run
and great for beginners). When completed, the
Powerhouse makes a docile model, and flies at a
beginner’s pace. As skills and flying prowess
advance, it is a very competitive model for the ½ A
Texaco event and can be a good first step to get a
novice into competitive flying. It teaches many of
the basic building skills needed to continue in the
hobby. These reasons (along with the fact that they
all seem to fly well) make the ½ A Powerhouse a
Figure 1 shows a completed 1/2 A Texaco Powerhouse
great choice. We want new flyers to be successful,
and the Powerhouse is a great platform to ensure that happens.
The ½ A Texaco event has no minimum weight requirements (like many of the other free flight events – I.E. most oldtimer free flight events have a minimum weight of 8 ounces per square foot of wing area). That means you can build as
light or as heavy as you want. Because there is a limited amount of power available from a reed valve Cox .049 engine,
keeping the model fairly light is a definite plus. The ½ A Powerhouse has a wing area of 540 square inches and can be
built light, with a low wing loading. . There are a lot of trade offs regarding weight and I try to put strength where needed,
and save weight where I can, within reason.
Getting Started
First of all, I order a plan. The ½ A Powerhouse plan is available from several sources, but we buy from Allen Heinrich
of Aerodyne. You can find Aerodyne at, 17244 Darwin, unit C, Hesperia, California 92345. His contact phone number is
(760) 956-2949 and his E-mail is [email protected] Aerodyne is a part time business, so call before going there.
Since this is a model that was published in the 1930’s, a copy of the original article is available from Society of Antique
Modelers (S.A.M.) Librarian Gene Wallock for a fee of $2.00. You can order the copy of the original construction article
from Mr. Wallock at: Gene Wallock, 13 Sandy Trail Lane, Lawton, Oklahoma 73505. I usually do this first to look over
construction methods and make sure I really want to build the model. Find a nice Cox reed valve engine. It is hard to
believe, but they are actually becoming more collectable now that Cox has quit producing them and they are fetching
collectible prices. One of the best sources to get one quickly is Ebay auction site, where there are always examples for
sale. Now that you have made the commitment and have these items, it is time to get to building.
Let’s build it
The first step in the building process is making the
parts, and I start by taking the building plan to a local
stationary store and make copies of the parts that
outline rudder, stab, ribs and wing tips (see figure 2).
These copies will be used as patterns to make the parts
necessary to build the model. One neat thing about
using the plan copies to make the parts is that the parts
will fit perfectly when placed back on the plan (when
doing the construction). Some plans come with a set
of patterns, but beware; they do not always match the
plan. This is especially true of older plans, that have
been copied multiple times, and distortion has
Figure 2 Shows copy of rudder outline
occurred. It is always a good idea to look over a plan and make sure everything looks correct. Make sure the wing will fit
the wing saddle; the stab fits properly on the fuselage, etc.
Do a take-off of the wood supplies that will be needed. The necessary balsa can be purchased from several balsa
suppliers. I always order more than I need so I can pick the weight of the wood I want for a particular part. There is a
selection of light wood known as “Contest Wood” and this should be used in several areas to save weight and help later
with the Center of Gravity. This will be explained more later, but most models tend to come out tail heavy, so building a
light rudder and stab will help this.
Now that you have your copies made and your supply of balsa
wood, you can start making the parts. Start by cutting out the
parts of the copies.
Then, using a
temporary type
glue stick put some
glue on the back
side of the paper
and paste them
onto the proper
thickness and
weight of wood
Figure 4 Line up grain and paste pattern to wood
(see figure 3).
Figure 3 Gluing back of pattern
Temporary glue sticks are available at most stationery stores. Most of the
plans show the direction the grain on the wood should go, and it is important to pay attention to this as you paste your
patterns on (see figure 4). I make all the perimeter parts out of contest wood. Contest wood is classified as 6 pound or
less per cubic foot. Using some basic math, and a good scale, you can calculate the “poundage” of all the wood you will
use. The reason I use light wood on these parts is because they are thick enough, that they do not need the strength the
heavier wood might add. Again, saving weight where you can is always advisable.
Once you have your paper pattern pasted
to the wood, you may want to stack
more than one part under the pattern.
Things like wing tips require two of
each part, so by stacking them, you can
make two at a time. You can either put
a tiny bit of CA glue between the parts
(very little so they can be separate later),
or use a straight pin through both (see
figure 5). Rough cut the parts around
the patterns and leave enough so they
Figure 5 cutting a second stacked part
can be sanded to the final fit. I use our
scroll saw to cut out the parts. It
helps a lot to have a scroll saw, but
the parts could also be cut out with
Figure 6 sanding inside radius
an X-acto knife or a sharp single
edge razor blade. I think it is much
safer, faster and precise to use a scroll saw. Mine is a Makita brand and I
bought it at a local hardware store for under $100. Once the parts are
rough cut out, they can be sanded. You can hand sand them, but I prefer to
use a stationary belt sander which I also purchased from the local
hardware. It has the advantages of keeping the parts square, and saving a
lot of time. I also utilize the round top portion of the sander to do inside
radiuses (see figure 6). One of the handiest tools I have for making parts is
Figure 7 handy disc sander
a small disc sander. It was custom made, and the exact type is no longer
available. Similar precision disc sanders can be had. It is also very handy all through construction (see figure 7).
One of the best things to come along in a while to add a lot of strength,
but not a lot of weight is carbon fiber, and I do utilize it in certain
applications. I like to apply a little medium CA glue, and rub the
carbon down with a paper towel to set off the glue and get a good
bond. Refer to figure 8 which shows me making a laminated spar for
the Powerhouse stab. The carbon is placed on one side of the spar, and
then the other side of the spar is placed over the top, sandwiching the
carbon. This is done by using ½ the thickness of the wood shown on
the plan. In example, if the plan calls for a 1/8 spar (as is the case of
the ½ A Powerhouse stab which is 1/8” x 1/2”), using the carbon built
up spar, use 1/16” balsa, carbon, and another 1/16” balsa. The carbon
Figure 8 building a carbon laminated spar
I use is a unidirectional carbon, .007” thick. I purchase it from
Aerospace Composite Products, web site:
http://www.acp-composites.com/ACP-CAT.HTM but it can also be ordered from several other sources including many
model hobby suppliers. By being unidirectional, it is very stiff in one direction, and is ideal for this type of application. I
glue about 6 inches at a time and wipe it down with a paper towel until it kicks the glue, and then lift the carbon and do
another 6 inches. This works great and is much easier than trying to glue the entire piece at once. Towards the end of
wiping the glue, a shot of CA kicker and more wiping will ensure the glue is fully cured. Because the Powerhouse stab
only has one spar, this lamination will help keep it from wanting to warp upward when the covering is applied. The stab
is supposed to be flat on the bottom, and sanded to an airfoil on top. The covering tends to pull the flat bottom up like a
truss as the covering draws tight.
Starting assembly
I build right over the plan, but only after I apply Saran Wrap or
Wax paper over the plan so the glue will not stick your parts to
it. Either works as a release for the parts. If you glue your parts
to the plan, you will have a real mess, so be sure to use one of
the above suggested. I like Saran Wrap, while my son prefers
Wax paper. As I said, either works fine.
I used thin CA glue for most of my building, and apply it
through a Teflon glue tip with a 1/16” outside diameter (Figure
9). These tips can be bought for about $.50 each and there are a
Figure 9 Gluing parts over protected plan
couple styles. One fits right over the stock glue bottle tip, and
then some is sold in 1-3 foot sections, and is inserted into the end
of the glue bottle tip. That is the type I use, cutting a 1” piece. It is helpful
to cut the side that will be inserted into the bottle on an angle to get it into
the tip easier. By using this tip, it really helps control the flow of glue.
Usually, only one drop is needed. Without using the applicator tip, the
glue just wants to run out. Try them; you will be glad you did. When the
part is all built with thin CA and has had time to cure, I pick the part up
and re-glue the joints
with just a little more thin
or medium CA (Figure
10).
Building the rudder for
the Powerhouse is pretty
straight forward. The
only modification I make from the plan is to add gussets to both side of
the rudder post as is visible in Figure 10. This helps to keep the glue
joint solid after covering. Without them, I have seen the rudder post
actually crush into the bottom of the rudder, and fail. When the
assembly is all glued together, I remove it from the plan and I re-glue
each joint with a small amount of medium CA for additional strength. I
Figure 10 re-gluing joints on rudder
Figure 11 sanding rudder flat both sides
only use a small amount, again being conscious of the overall weight. When dry, I sand both sides to get it flat and then
sand a uniform symmetrical airfoil to the leading and trailing edge (see figure 11).
The stabilizer construction is done in much the same fashion as the rudder.
After I have it built, and have re-glued all the joints, I sand the bottom of it
flat. On the stab, a lifting airfoil is sanded on the top of the stab (refer to
plan). When done right, it will have a flat bottom lifting stab.
The first step in building the wing is making the wing ribs. I use a copy
made from the plan
and affix it to a
piece of 1/8”
plywood. I then
temporarily glue
Figure 12 the start of rib templates
another 1/8” piece
of plywood to the
first and drill two 1/8” holes through both pieces of plywood
(see figure 12). I insert 1/8” dowels in the holes to hold all my
ribs between the two completed templates and the holes will act
as a vent when the wing is constructed. I sand and finish the two
plywood templates to the outline and separate them. Now, they
are ready
to be used
Figure 13 drilling holes in roughed out balsa ribs
to make
ribs. I
rough cut (oversize) my balsa ribs and a few at a time, drill the 1/8”
holes through them, using one of my 1/8” rib templates as a guide
(see figure 13). I can usually stack ½ of the needed ribs between the
templates at a time to finish them, making all my ribs in two batches.
With half the ribs sandwiched between my two finished templates,
and 1/8” dowels
running through all, I
sand the balsa ribs to
the shape of the
templates. When that is
Figure 14 cutting notches for spars
done, I am ready to cut
in my spars notches. I
have a Dremel and a Micro-Mark table saw, and both work well for this
operation. Before I had the saws, I would cut them in using a Zona saw and
assorted files to get them to the correct size. With a table saw, I make several
passes adjusting a little
at a time to get the
correct notch width (see
figure 14). I also use a
cheap set of calipers to
keep checking the notch
size. When all the
notches are cut, I am
ready to repeat these
steps to make the other
Figure 15 making trailing edge
batch of ribs.
Figure 16 shows 3/8" balsa tips installed
While you can buy off the shelf trailing edge, I like to make my own
(see figure 15). This allows me to make it at the correct angle to
match my ribs and saves a lot of sanding later. I make my wing tip parts out of real light 3/8” balsa. This extra thickness
may add a little
weight, but
makes the
shape of the tip
much better
and makes it
much easier to
cover when
completed (see
figure 16). The
tip is glued on
flat, but the
Figure 17 trailing edge is notched for ribs
Figure 18 the 3/8" tips allow complete shaping
front of the
trailing edge is
lifted to match the curvature of the rib which is not flat on the bottom. When the wing tips are glued to the wing, note that
they are not flat on the plan, but are actually up in the air as they are lined up with the center of the leading edge and the
center of the trailing edge. This is correct. When
sanding the tip to shape (see figure 18) a useful tip is
to put masking tape on the ribs so you don’t
accidentally start sanding them away. You use the
ribs as a guide, but do not want to remove any
material from them. Also note in figure 18 how the
spars are cut and glued from the last rib to the tip.
The wing’s center ribs are cut down 1/16” on top and
bottom. This area is to be sheeted with 1/16” medium
weight balsa. In the last few years, I have been
utilizing .007 unidirectional carbon fiber at my
dihedral joints as doublers (see figure 19). I have had
real good luck with this method and it is very light.
Using plywood or hard balsa doublers will work okay
Figure 19 shows carbon fiber doublers for the spar joints
too, but is a little heavier. The spars in the wing are
picked and matched for weight. I try to use a medium
weight of 8-12 pounds for the wing spars. It is important to match the weight and strength of the spars for the balance of
the wing and for the longevity of it. While the wing does not have to be as strong as those on bigger and faster models, it
does have to be strong enough to
withstand the impact of
dethermalizing.
Figure 20 wing on my hinging dihedral jig
The Powerhouse has a flat center
section, and both wing panels are
attached at the appropriate angel
and glued to the carbon doublers as
well as in the butt-joint as shown in
figure 19 and 20. I have made a
special hinging board to set the
dihedral joints. Not only does this
allow me to set the angle correctly,
it also ensures that the wing remains
straight and that the wing panels are
not sweeping forward or back. The
jig is made with a piano hinge and
5/8” birch plywood (figure 20). I
just use whatever is handy to space
it up to the correct angle.
The Fuselage on the Powerhouse is a
basic box frame construction. To get
started, I weigh and find four
medium/hard balsa longerons, 12-14 lb.
wood. By matching the strength and
weight of the longerons, the fuselage will
build more uniform and will be strong.
Balsa, weight and strength do tend to go
hand-in-hand. If you did not take the time
to match your longerons, the weakest will
bend the easiest, and the strongest will try
to go back to the natural straight shape.
This will cause the fuselage to be shaped
like a banana, which is not what we are
looking for.
Pin down the longerons and start making
your cross pieces. For this, I use my disc
sander get the final size, and make two
parts at a time so when I am ready to build
Figure 21 shows one fuselage side on plan, note calipers, scale & angle finder
Figure 22 One side glued up
Figure 23 sanding both sides flat
the second half, I already have all the pieces made
and they are exactly the same as the first side.
Figure 21 shows my first side made and the extra
corresponding part for the second side above the
first side. I start making my cross pieces
(diagonals) in the front where they are the longest.
If I make a mistake and one gets too short, I simply
use it for the next smallest part. The parts get
smaller as you work towards the back. When all the
diagonals are glued and the sheeting for the engine
cheek is glued in place, I again lift the side off the
plan and go over the joints with a little medium CA
glue (see figure 22). Build the other side following
the same steps and then sand both of the sides flat
(see figure 23). I use a drum sander to sand the
Figure 24 sanding the corner of the windows round
curves in the corner of the window frame (see figure
24). This makes for a nice looking curve, very
uniform. I sometimes will also make sanders, by wrapping sand paper around tubes for sanding similar inside radius.
The front of the cabin, where there is an upright, is a weak
spot because the upright is bisected by the bottom outline
of the window. To add strength in this area, I glue a piece
of .007 thick unidirectional carbon fiber full height. This
helps support the joint, and I have never had one break
since using this method. You can also add another
upright, full height, to the inside where the carbon is glued
in figure 25. Remember you are making a left and right
side, so be conscious to glue the support to the correct side
on each fuselage side.
I am now ready to join the two halves. I start at the front
Figure 25 carbon fiber added for strength on upright
where the fuselage cross pieces are all the same length and
make eight parts exactly the same length. I tape one side
to a square, so I am sure it is straight up and down. I
weight the sides down to the plan using lead weights (see
figure 26). This gets everything square, and
perpendicular. I also do this right over a top view. The
Powerhouse plan does actually have a top view, it just
specifies a width. So, I draw a top view on the back side
of the plan, starting with a center line.
With the sides rigged as shown in figure 26, I start gluing
in the cross pieces. I glue in the bottom and the top cross
pieces that I made earlier to the same length. After these
are glued in place a dry, I pull the sides together in the back and this creates a natural flowing curvature. I sand the inside
of both sides a little at the back so they can be
lined up and glued together. This is where the
center line is very handy, as the back of the
fuselage should line up exactly over the center
line when glued together. This will ensure a
straight fuselage. Then, I make the reaming cross
pieces to fit the curvature created by gluing the
two sides together at the back. Be sure you do not
sand them too thin at the back, as this is where the
dethermalizer and snuffer (tubing used to snuff
out the dethermalizer fuse) tube will be added
later.
Figure 26 joining the two fuselage sides
The firewall is made from 1/8” aircraft grade
birch plywood. I use a modified countersink drill
for the four 4 x 40 blind nuts placed in the firewall
to mount my tank (see figure 27). This allows me
to slightly countersink the blind nuts in and get
Figure 27 firewall, tank-mount, countersink, blind nuts
good glue joint. I press the blind nuts in after
using Super Seam (an adhesive used to attach
covering to metal and wood on full size aircraft) as glue. When it is dry, I go over it again with another coat of Super
Seam. You want to be sure to get these glued in well, as you never want them to fall out. Super Seam can be purchased
from Aircraft Spruce, 225 Airport Circle, Corona, California, 92882. Their phone number is 951-372-9555. They are a
supplier for home-builts and general aviation. Note the ring I added in figure 27. This was done so the blind nuts did not
protrude through the front of the firewall when glued in place. Also note, it is offset to the side, so the prop will be more
centered when we add left thrust. Before gluing
the firewall in place, it is always a good idea to
chase the threads with a 4 x 40 tap to make sure
no glue got into the threads. Sal Taibi used to
make the tank mounts like the one shown in figure
27, but no longer does. The current SAM rules
allow for 15cc of fuel, but the rule cycle is due to
be voted on again, and there is a movement to go
to 8cc (the size of a stock Cox Texaco tank). It is
beneficial to run a tank-mount as shown. It spaces
the engine out to the proper location (without it, a
spacer will have to be made to get the engine
where it needs to be). Getting the engine in the
proper location will really help with balancing
your model as they almost always come out tail
heavy. Cox engines have an o-ring in them that is
in the middle of the tank. When the tank is full,
the o-ring is submerged in fuel. When it gets
down to a half tank, it starts to be surrounded by
air. Many times, this will leak and cause your
engine to lean and only run ½ the tank and the
engine will stop.
Figure 28 shows landing gear in place
I bend the landing gear and glue it up between
balsa sheet wood. When completed, the
sandwiched gear should line up with the fuselage
uprights, where it can be secured well (see figure
28).
The hood (part that fits behind the engine is
formed by wetting a piece of 1/16” balsa and
taping it around a cylinder. I used a can of spray
paint to wrap mine around, and secured it using
masking tape until dry (see figure 29). By
Figure 29 the formed hood for the Powerhouse
performing this part, it will take the bind out of it
for fitting and is much less likely to crack later. I
soak the wood in water, but some prefer to add a little ammonia to the
water thinking it helps with the bending process. I have had good luck
with just using water, and don’t have to smell the ammonia. Either will
work. When it is dry, I fit it and glue it to the fuselage. The nose block
under the engine can be fit and glued on now using medium balsa. Make
sure you can reach all the screws that hold the tank to the firewall. About
the last thing to add is the sun visor. After shaping and sanding the nose
cowl blow out the dust and fuel proof the inside area. I use slow drying
epoxy thinned a little with lacquer thinner. A little thinner goes a long way.
I mix and brush it on with an acid brush, being careful not to get any in the
blind nuts. It may take a few days to dry. A warm climate or room helps. I
then sand this area the best I can and brush on another coat. This makes a
shiny and smooth fuel-proof engine area.
COVERING WITH POLY SPAN
I cover all my gas models with Polyspan as it is light and provides a
strong, long-lasting finish. I also like how stable it is. Since it is a
polyester base material, it is not affected by moisture like many of the
other coverings, like silk, or tissue. Polyspan is excellent and helps you
have that consistent model you are looking for, with no surprise warps
Figure 30 brushing on sanding sealer
showing up. Polyspan has a smooth side and a
rougher side, where the fibers stick up. It is very hard
to see the difference, but the smooth side is a little
shinier, and with careful inspection, you can see the
fibers on the rough side. The smooth, shiny side goes
out and is the finish side. As of now, the only color
that Polyspan comes in is white (natural).
To prepare the surfaces to be covered, I make sure all
are sanded smooth and are blown clean. I brush on a
coat of lacquer sanding sealer (see figure 30)
everywhere the covering will contact the structure.
That means the top and bottom of ribs, all the
perimeters, etc. I finish exclusively with nitrate dope,
and have found the lacquer sanding sealer to be
compatible. If you plan to use an alternative finish,
make sure everything is compatible by making a test
panel. After my sanding sealer is dry, I sand all the
surfaces with 220-320 grit paper and again blow the
surface clean with compressed air. I then add a second
coat of sanding sealer and sand it with 320 paper. You
will notice the second coat will sand much easier and
you will have a very smooth surface. Blow the dust
off the structure.
There are a few products that can be used to attach the
covering to the surface, but I have been using Fab Tac
also available from Aircraft Spruce (contact
information noted previously in this article). The
Super Seam used to glue in the blind nuts works great
too. I have found the Fab Tac works just as well as the
Super Seam, and is about half the price. Both products
need to be thinned a lot using Nitrate thinner to get to
brushing consistency.
Figure 31 covering on wing tip, note wrinkles
Figure 32 covering attached to spar with Acetone
I brush on two coats of thinned Fab Tac
over all the areas I used the lacquer sanding
sealer on (where the covering will contact
the framework). It dries fast, so you will
have to work fast. Make sure to let it dry
fully between coats. When both coats are
dried, I make sure there are no defects in it
like a run. If I find a defect, I lightly sand
that area, and clean with compressed air.
Now, I am ready to cover.
I usually start with the bottom of the stab. It
is always correct to cover from the bottom
to the top on all parts. The flat surfaces are
very easy to do. Do not forget the fuzzy
side goes towards the frame work, and the
smooth side out. Cut your Polyspan larger
than the area to be covered. You want extra
material to hold onto around the perimeter if
heating is necessary to get it smooth.
Figure 33 covering attached between wrinkles from extra covering
Figure 33 again shows wrinkle to be shrunk with heat
Polyspan can be stretched and shrunk with heat and
will go around some severe compound curves. To
attach the covering, lay it over the structure and use
Acetone in a brush to activate the Fab Tac on the
framework. By brushing the Acetone through the
covering, it will soften and activate the Fab Tac, and
will adhere quite quickly. Try to work out as many
wrinkles as possible as you are attaching the Polyspan.
Figure 34 I use a MonoKote heat gun to shrink out wrinkles
For purposes of showing the stretching and shrinking
capability of Polyspan, I will show the top of the
Powerhouse wing tip (figures 31-34). I attach the
covering at the root, and then pull it and attach it
down the spar (see figure 32). Because the tip is a
compound curve, there is an excess of material
when you start attaching it around the perimeter.
The way I do this is to pull it and attach it in small
sections, leaving the excess material in between
several points where I attach it (see figure 33). I use
a MonoKote heat gun to shrink the material between
the points of attachment (see figure 34). Make sure
you let the Acetone gas out before doing this (dry),
or it will bubble the Fab Tac as the Acetone is
heated. I go one wrinkle at a time, and after it is
Figure 35 a completed wing tip shrunk and attached
Figure 36 sanding off the extra covering
shrunk down smooth, I attach it with Acetone. Now you can see
why I cut the Polyspan oversize so I do not get burned when
shrinking. One useful tip is to start shrinking the material
outside the framework and work inward. By working one
wrinkle at a time, I get a very nice finish on my compounding
curves (see figure 35). I like to attach around the perimeter and
shrink all the covering over the surface before attaching to the
ribs. Make sure you stick it well to the bottom ribs, where there
is under camber. Here, I will hold it against the camber with my
fingers until the Acetone dries, which only takes a few seconds.
Also, make sure it is attached to the top of the ribs and all spars.
After the covering is attached to the perimeters, ribs, and spars, I roll up a piece of 320 wet-or-dry sandpaper and use it to
trim off the excess covering (see figure 36). Make sure you have allowed adequate time for the Fab Tac and Acetone to
dry before doing this.
Whenever Polyspan is lapped over itself, like at the dihedral joints of the wing, brush on two coats of Fab Tac over the
first layer where it will be overlapped by the second layer. This will ensure a good positive joint, and the covering will
not split away. I also use full strength Fab Tac or Super Seam to attach the rudder to the stab after both are covered. It
makes a good joint as both glues are designed to glue fabric to wood or metal, so it is the best choice.
After finishing the wing
covering, I drill a small hole
through the center section
sheeting (bottom) to vent the
wing. Remember the holes in
the ribs that were made
during the scratch building
process? Well now they act
as vents and allow the wing to
vent tip to tip. Without a
vent, the wing would tend to
blow up like a balloon when
put in the sun at the flying
field. Venting adds to the
stability of the covering and it
is much less-likely to warp by
doing this. On the rudder
and stab, I use a straight pin
to poke small holes (on the
bottom of stab, and one side
of rudder) in the corners of
the structure to vent them as
Figure 37 heat is used around all compound curves, like the front of fuselage
well. Like I said, this is a
very important step in the
covering process. Remember, heat can be used to stretch and shrink Polyspan, and the heat will help you achieve a good
covering job over all compound surfaces (see Figure 37).
Applying the Nitrate Dope
When all the covering is attached and shrunk tight with a heat gun, I am ready to apply my nitrate dope. There
are two types of Nitrate dope, standard (tautening) which means it draws tight as it cures, and non-tautening
which does not draw as it cures. Be cautious in using too much standard dope especially on a light structure
where it can actually cause crushing and severe distortion. Most dopes are thinned 50/50 with nitrate thinner
to get a good brushing consistency. I use a specific brand of foam brush to apply the dope, a 3” wide Jen (brand
name is Jen) brush. It says not for use with lacquers, but works great as long as the entire brush is not
submerged in the thinned dope. I only wet about the last 1” – 1 ¼” of the brush in the dope.
I start by applying a coat of standard (tautening) dope over the entire covered area. This helps keep the
covering tight. I then put a second coat of standard on the bottom of the wing. The wing and stab tend to want
to warp up, as the airfoil acts a truss, and pulls against the bottom which is flat or near flat. When completed, I
apply 4-5 coats of clear nitrate. On the bottom of the stab, I use all standard nitrate. All the other coats, except
those noted, are done with non-tautening. I move the brush slowly, and do not apply a lot of pressure.
Remember, you are trying to apply the dope, not squeeze a bunch through the covering. This will only add
unnecessary weight. As you start getting dope built up, you may notice the brush grabbing on the leading edge
and trailing edge. If this happens, you can sand those areas with 400 sandpaper. DO NOT sand the Polyspan
between coats, as it will only pull fibers up and mess up the finish. After your 4-5 coats of dope are applied,
you can very lightly sand the surface if you want but it is not necessary. If you want to put your AMA number
or other decorative tissue on your model, apply it after 3 coats of dope, and put at least 3 coats over the top of
your tissue to seal it as well.
I cut my letters from Japanese tissue. I use 3M fine Line
tape as a reference and hold them in place with a pair of
tweezers and spray them with water, one at a time. Now
final position it and blot out as much water as possible
with a paper towel. As soon as I am finished blotting, I
start brushing on a little acetone. The acetone keeps the
letter locked down until water evaporates. Keep it
acetone wet until all of the water has evaporated. Repeat
this process with all your letters. As you become more
proficient, you can start doing several letters at a time.
The Powerhouse decals on the side of the fuselage were
scanned from an old article and made on the computer.
Wire Fittings and dowels
Some hardware is necessary now, like the wing and
stabilizer keys, the dethermalizer hooks, and the snuffer
tube (See figure 38). The two wires with the large radius
are for the top of the stab, and the large radius is
intentional to get more leverage to pop up the stab in
dethermalizer mode. The other two wires go on the back
of the stab and the back of the fuselage. This is where I
wrap a rubber band around the dethermalizer fuse. The
snuffer tube also goes in the back of the fuselage, between
the two wires. The wing and stab keys are made from ½
round made from dowel. I like to round the ends also as I
think it looks better. I glue the wires and alignment keys
with Fab Tac, at near full strength.
Now cut the 3/16” dowels the rubber bands loop around to
hold the wing and stab to the fuselage. They should stick
out of the fuselage about 5/8” on each side. Make sure
your wing is square before gluing the keys on. Put the
wing on with some #64 rubber bands, and measure from
the tail to a spot on the wing tip on both sides. If the
measurements are the same, the wing the wing should be
square to the fuselage and you can glue on your keys.
Next, glue the four dowels to the bottom of the stab (with
stab installed). Don’t forget, the rudder is supposed to be
offset for glide turn.
Figure 38 shows the dethermalizer hooks, wing keys and
snuffer tube. Also, I make a hole-saw out of brass tube to drill
wing hold-down dowel holes
Figure 39 one side of fuselage masked as described with 3M
Fine Line and 3M Scotch 233+ masking tape. Works great!
Now for the Paint
I really like the looks of the Powerhouse paint scheme, and have followed it on each of them I have built. To get nice
sharp lines, I mask the paint scheme with 3M Scotch Fine Line (a tan colored product). It is available in many widths,
conforms to sharp corners, and sticks well. It is very good to stop bleed under, where paint bleeds under the tape, and
leaves a soft edge. After I have the outline of the paint scheme down with Fine Line, I use newspaper and 3M 233+
(green) masking tape to cover the areas I do not want painted (refer to figures 39 and 40). Both products were developed
for the automotive paint industry and are resistant to chemicals like thinner and most types of paint. If you use the wrong
type of masking tape, you will run the risk of it lifting as soon as the paint hits it, or maybe worse, the adhesive being
attacked and becoming a permanent part of your model by not being able to peel it off! In any case, I have found the
233+ to be the best masking tape available. These 3M masking products can be purchased from any automotive paint
supplier. A tip on using the newspaper is to use two layers in case there is an imperfection. This will eliminate paint
getting where you do not want
it. Also note, one side always
has small holes used in the
printing process so be sure to
tape over them, or not use that
side where possible. After
everything is masked and
before painting, I always rub
down the edges good before
applying color.
Colored Nitrate is almost
impossible to get. The one
source for colored Nitrate is
Aerodyne (Allen Heinrich)
whose contact information was
listed earlier in this article. He
Figure 40 Fine Line and 233+ masking used on the stab as described. Note the rudder
sells a good selection, with
offset and how the paint scheme is also offset to match
white, black, red, yellow, cream
and blue among other colors. His colors are opaque and cover quite quickly. Many times, I am after a translucent look,
and have had excellent luck mixing House of Kolor (another automotive paint product) Kandy Koncentrate with thinned
clear dope. When I mix my
colored dope, I always use
non-tautening dope, thinned
to spray consistency with
Nitrate thinner. House of
Kolor offers a good selection
of colors, and I like red,
pagan gold and tangerine a
lot. A small quantity (about 1
ounce) of Kandy Koncentrate
will color enough dope to
spray a good size model.
I spray on a couple light coats
using a cheap touch up gun.
Since the color intensity
builds with more coats of
paint, putting it on even is
important. It helps to spray
each coat in perpendicular
directions, called cross
Figure 41 Masking is stripped after nitrate dried, ready for fuel proofing
coating. We spray with 50-60
pounds of air pressure. For
this model, I mixed up a maroon in clear non-tautening dope. When stripping the masking, it helps to pull it back against
itself to keep the sharp edge. After painting and stripping masking, it is ready to be fuel proofed, which will protect your
new paint job from being attacked by fuel with nitro content.
Fuel Proofing
I have used a product called Fullerplast, developed by Fuller O’Brien paint products as a bar top finish. It works great for
fuel proofing model airplanes. I used to be able to buy it locally, but more recently, have had to order it on the internet
from Van Dee at http://www.van-dee.com/clear.htm It is a 2-part product, with a clear and a catalyst, mixed in a 16:1
ratio. Fullerplast comes in two forms Gloss and Satin. Both work and it comes down to personal taste. I actually use
both, and on some of the old timer
models think the Satin makes it look
more period correct. That is what I
will use on this model. I use a digital
scale, and mix my 16:1 ratio of the
Fullerplast by weight. It is ready to
shoot when mixed, and no thinning is
necessary. I shoot one heavy coat of
Fullerplast using 60 pounds of air
pressure and the same cheap touch up
gun I use to paint with. The stuff is
really sticky, but can be cleaned up
with Lacquer thinner. It dries kind of
slow, so be sure to not shoot it too
heavy or it will run. I would suggest
shooting a test panel before trying it
on your first model. I have found that
I can store any left-over Fullerplast in
a glass jar in my freezer for up to 9
months, so you do not have a lot of
Figure 42 one side of windshield glued and drying. Note paper windshield
waste. The cold temperature cancels
pattern in foreground
out the chemical reaction. Before
using it the next time, just let it come up to room temperature, as it gets thick when cold.
Installing Windows
For the windshield pattern, I fold a piece of
paper in half and use the S.W.A.G. (Scientific
Wild A** Guess) method until I get a pattern
that fits the fuselage. This may take a couple
tries. When the pattern is made, I lay it on a
piece of .016 Butyrate plastic and trace around
the outside edge. I use a pencil that is made to
write on almost anything, paper, glass, plastic
and metal. The brand is Stabilo and it is part
number 8008. I bought mine from a stationery
store. Cut to the line and test fit the window to
make sure it fits right. The side window
patterns are easy to make by using the fuselage
as a guide.
I use Formula 560 canopy glue to install the
windows. I don’t think anyone likes installing
the windows, but patience and learning
technique will yield a good installation. The
Figure 43 side window is set in place over a small bead of Formula
560 glue. Set in place to avoid smearing glue
glue is white when applied, and dries clear. Do
not get in a hurry to remove clamps and tape, as
it takes a while for the glue to cure completely (refer to figure 42). For flat windows like the side windows on the
Powerhouse, I lay down a small bead of glue and set the window into place. Make sure you have the fuselage lying flat so
the Butyrate plastic will not slide out of place. Be careful when you set the plastic that it is in place, and you don’t smear
the glue.
Finishing Up
I install the #8 Trexler tires by soldering on a small washer on the outside of the wood hub (see figure 42). Glue in the
dethermalizer fuse snuffer tube and the hooks in the back of the stabilizer and fuselage (Use Fab Tac glue). When I bolt
the engine in, I like to use a small amount of blue Loctite on the threads so the screws will not vibrate loose. The thrust
on the Powerhouse is about 3 degrees of left, and about 3 degrees of down. This will induce a left hand climb, and
overcome the right offset in the rudder. The desired flight is left hand climb, and right hand glide. I like this pattern
because you can tell when the engine shuts off as it switches from left hand to right hand. On a 15cc flight, they will run
about 13 minutes under power, and it will be VERY high. The last step is to check for warps and trim. I try to have my
stabilizer flat, and store it on a 2” thick Styrofoam board (rubber Banded to it). This will help keep it flat, and is light, so
if you drop it by mistake, it will not break. Some guys use wooden boards for the same purpose, but you can imagine
what would happen if you accidentally dropped it with the weight of a board attached to it. On the wing, I like to washout both tips. That means, looking from the back of the wing, the trailing edge is lifted about 3/16”. This adds a lot of
stability to the flying. The desired wash-out can be induced by again heating the Polyspan covering with the MonoKote
heat gun and holding pressure to twist the desired warps into the wing or stab.
I keep a notebook with all of my models and their
trim specs. It is an excellent reference, especially if
a model requires repair and you want to know how it
was set up. I update the trim notes as I make changes
to the model. The trim sheet for my ½ A
Powerhouse is shown on the next page. It will give
you an idea of the things I keep track of.
I buy all my fuel from Aerodyne as they offer an
excellent selection of fuels. I have found on hotter
days, I can run less nitro (5-10%) than on colder days
which requires higher nitro to keep the wick lit! On
cold days, I use 25% nitro fuel. There is an
advantage to running the lowest nitro possible. It is
more economical and will net a longer engine run.
This is a great beginner free flight model. If you are
a raw rookie, it is always advisable to get help with
your early flights. That is how most of us learned to
fly. I was lucky enough to join the SCAMPS and the
Perris group of flyers, and learned a lot of what I
know from Sal Taibi. I do not think anyone has
taught more modelers to fly than Sal. I thank him for
everything he has meant to me. When someone is
helping trim your model and suggest changes, have
them explain why they think it needs these changes.
That is a method to learn.
I hope this article has enticed you to build a ½
Texaco Powerhouse. If it has, you will be building a
Figure 44 Ready to make a flight at the SAM Champs, Henderson
fun airplane, and when it is all set up, will make a
Nevada. Note the long fuse hanging from back of model.
fun competition model too. Texaco and ½ A Texaco
are my two favorite events to fly and I have had
more fun flying these events than any others. Good luck and get ready to have an excellent flying, competitive free flight
model.
Suppliers and References
Aerodyne – fuel, paint, general free flight supplies
17244 Darwin, Unit C
Hesperia, California 92345.
Phone (760) 956-2949
E-mail is [email protected]
SCAMPS Southern California Antique Model Plane Society – Southern California flying club
Web Site http://scamps.homestead.com/
SAM Society of Antique Modelers – Governing body for old timer free flight
Web Site: http://www.antiquemodeler.org/index2.html
Aerospace Composite Products – Carbon fiber supplies
Web Site: http://www.acp-composites.com/ACP-CAT.HTM
Van Dee – supplier of Fullerplast for fuel proofing
Web Site: http://www.van-dee.com/clear.htm
Gene Wallock – Sam Librarian where you can order a copy of the original build article (for full size Powerhouse)
13 Sandy Trail Lane
Lawton, Oklahoma 73505
Aircraft Spruce, 225 Airport Circle, Corona, California, 92882
E-mail: [email protected]
Aircraft Spruce – supplier of adhesives used for gluing and covering and general aviation supplies
225 Airport Circle
Corona, California, 92882
Web Site: http://www.aircraftspruce.com/
Larry Davidson – general free flight model supplies including Polyspan
66 Casa Mia Circle
Moneta, Virginia 24121
E-mail: [email protected]
Gary Sherman
1521 S. Normandy Terrace
Corona, California 92882
E-mail: [email protected]
After completing this model, I won the ½ A Texaco event with it at the
2005 at the SAM Champs, Henderson, Nevada. My three flight total
was almost 74 minutes and lots of fun, and lots of chasing!
My ½ A Specifications sheet below
½ A Texaco Specifications Sheet
Class: ½ A Texaco
Model Design: Sal Taibi’s Powerhouse
Engine: Cox Texaco .049
Thrust: 4 degrees of left, 2 degrees of down
Propeller: Cox Grey 8 x 4 Texaco Prop
RPM: 7,200
Fuel: Aerodyne Custom 100 (10% Nitro)
Weight: 19 ounces
Wing Area: 540 sq/in.
Wing Loading: 5.06 ounces/square foot
CG: 5 1/2” Behind Leading Edge
Incidence: 2 degrees
Trim in Wing: 3/16” wash-out both wingtips
Stab Tilt: none
Rudder Tab: none
Flight Pattern: Left/Right
Special Notes: Model runs about 13 minutes on 15cc of fuel. Use Custom 250 fuel on cold
days, Custom 100 on warm days.